1. Field of the Invention
The present invention relates to a method for drying a semiconductor wafer, a mixture for drying the same, and a dryer for drying the same.
2.Description of the Related Art
Lower alcohol may be used to dry a semiconductor wafer cleansed with pure water or the like.
Such lower alcohol to be used for drying is usually isopropyl alcohol (IPA), because of its high volatility, low toxicity, and cheapness.
However, as circuits formed on semiconductor wafers are more and more miniaturized, defects caused by alcohol left on the surface of those products after drying are found more frequently.
It is reported in xe2x80x9cExtended Abstracts of the 1997 International Conference on Solid State Devices and Materials, Hamamatsu, 1997xe2x80x9d, pp24-25, that a gate oxide film may be deteriorated if IPA of more than 2 ng/cm2 is left on a semiconductor wafer. As for the reason why so much of IPA is left on a dried semiconductor wafer, a possible cause may be that molecular weight of IPA is relatively heavy, as much as 60.
A technique for drying a semiconductor wafer with using alcohol is disclosed in Unexamined Japanese Patent Application KOKAI Publication No. S62-142328, Unexamined Japanese Patent Application KOKAI Publication No. H8-61846, and Unexamined Japanese Patent Application KOKAI Publication No. H11-102890.
Specifically, in Unexamined Japanese Patent Application KOKAI Publication No. S62-142328, a technique is disclosed which is for removing water from a semiconductor wafer by reducing surface tension of water with using an organic solvent having surface tension half that of water.
In Unexamined Japanese Patent Application KOKAI Publication No. H8-61846, a technique is disclosed which is for pouring IPA on a semiconductor wafer cleansed with water, and volatilizing an azeotrope of water and IPA on the semiconductor wafer with using hot nitrogen gas.
In Unexamined Japanese Patent Application KOKAI Publication No. H11-102890, a technique is disclosed which is for removing water on a surface of a semiconductor wafer with higher alcohol, and removing the higher alcohol with lower alcohol to dry the wafer.
However, a technique for suppressing the amount of alcohol left on a dried semiconductor wafer to 2 ng/cm2 or less is disclosed in none of those publications.
The contents of Unexamined Japanese Patent Application KOKAI Publication No. S62-142328, Unexamined Japanese Patent Application KOKAI Publication No. H8-61846, and Unexamined Japanese Patent Application KOKAI Publication No. H11-102890 are incorporated herein by reference.
Accordingly, it is an object of the present invention to provide a method, a mixture used for drying, and a dryer for drying a semiconductor device which realizes a high yield of semiconductor products. And it is another object of the present invention to provide a drying method, a mixture and a dryer for suppressing an amount of alcohol left on a semiconductor wafer to 2 ng/cm2 or less.
To achieve the above objects, the method for drying a semiconductor wafer according to the present invention, which is for drying a semiconductor wafer cleansed with water, comprises drying a semiconductor wafer by supplying alcohol whose mean molecular weight is 46 or less to a surface of the semiconductor wafer.
According to this invention, a high yield of semiconductor products can be realized.
The alcohol may be a mixture of lower alcohols.
The alcohol may be made of at least two of methanol, ethanol, and isopropyl alcohol.
The mixture used for drying according to a second aspect of the present invention, is a mixture which is to be used to dry a semiconductor wafer cleansed with water, wherein the mixture is made of two or more kinds of alcohols, and has mean molecular weight which is 46 or less.
The mixture may be made of at least two of methanol, ethanol and isopropyl alcohol.
The dryer according to a third aspect of the present invention comprises:
a room for drying a semiconductor wafer cleansed with water;
a holder which is arranged at a predetermined position in the room, and is for holding the semiconductor wafer; and
a supplier for supplying a mixture for drying the semiconductor wafer to a surface of the semiconductor wafer placed in the room,
wherein the supplier supplies the mixture which has hydrophilicity, volatility, and mean molecular weight which is 46 or less.
The mixture may be made of two or more kinds of lower alcohols.
The mixture may be made of at least two of methanol, ethanol, and isopropyl alcohol.